The present invention relates to photoelectric intrusion detector systems of the type including a transmitter unit which projects a beam of optical radiation, as, for example, infrared energy, and a receiver unit which contains means for detecting said optical radiation. Generally, the interruption of the beam of optical radiation indicates the presence of a person or object, and may operate a door or an alarm signal. It is well known that the transmitters and receivers of such systems must be optically aligned with each other. The present invention relates to such alignment of transmitters and receivers.
Some prior art systems of this type have used a visible light at the transmitter or at the receiver for purposes of aligning the optical systems. This often requires installation under low-light conditions so that the projected light is visible for alignment purposes.
It is an object of this invention to provide a photoelectric intrusion detector system of the type discussed above in which the need for an alignment light is eliminated. It is a further object of this invention to provide an intrusion detection system which is easily aligned under ambient light conditions.